Animal remedies for sheep, cattle and the like are applied by a number of methods including topical or “pour-on” application, oral application, injection and nasal infusion. Each of these is typically dispensed from a “pistol grip” style dispensing means. One such dispensing means of the prior art is shown in FIG. 1.
As is common with applicators of the prior art the applicator has a piston or plunger 2 which can be reciprocated within a barrel 3 by squeezing and releasing a first handle 4 relative to a second handle 5. The liquid to be dispensed is drawn into the barrel 3 through an inlet 6 via a one way inlet valve 7 when the plunger 2 is withdrawn inside the barrel 3, and is dispensed through a nozzle 8 via an outlet valve 9 when the plunger 2 is extended towards the outlet valve 9.
In the dispensing means of this type the outlet nozzle 8 (or needle if the dispensing means is an injector) is substantially aligned with the central axis of the barrel 3, and the barrel 3 is orientated approximately transverse to the first handle 4. As a consequence, the outlet of the nozzle is typically substantially parallel to the forearm of the user when the dispensing means is in use, at least when the user's wrist is in a relaxed position.
When applying an animal remedy to an animal, particularly in an oral formulation, the user of the dispenser typically approaches so that he or she is facing, in substantially the same direction as the animal, if necessary the animal's read is restrained, and the dispenser is orientated so that the nozzle is inside the animal's mouth. The dispenser is then activated and a measured dose of animal remedy is dispensed into the animal's mouth. It is preferred that the outlet of the nozzle is behind the animal's tongue, to ensure that the majority of the remedy is swallowed.
The position of the user relative to the subject animal means that he or she must bend their wrist and elbow to a considerable degree in order position the nozzle in the correct position in the animal's mouth. This can be uncomfortable, and can be fatiguing if a large number of animals must be dosed.
Some dispensers of the prior art, such as the one shown in FIG. 1, have nozzles which incorporate a small bend, for example around 30°, in order to position the outlet in a more suitable orientation. While this is an improvement over straight nozzles, it does not alleviate the problem.
An additional disadvantage of the pistol grip style dispenser is that the nozzle outlet is often a considerable distance away from the user's hand. This impacts on the user's ability to determine the position of the nozzle in the animal's mouth, and also increases the force which must be used to correctly position the nozzle if the animal is resisting. This can lead to further discomfort for the user, and to injury to the animal.
As can been seen in FIG. 1, the outlet valve 9 is substantially aligned with the central axis of the barrel 3. This means that any bubbles in the fluid may become trapped in the barrel, as bubbles tend to accumulate at the top of the barrel 3 and therefore fail to pass through the outlet valve when the fluid is dispensed, if the bubbles cannot be purged from the barrel then the dose dispensed by the applicator will be incorrect.
Many animal health dispensing means of the prior art are provided with means of adjusting the dose dispensed when the applicator is used. In many applications it is critical to the health of the animal that the correct dose is applied.
One example of such a device is that described in New Zealand patent No 521084. As is common with such devices, the dose is adjusted by rotation of a dose adjustment dial, referred to as a “dosage control part” in the patent specification.
Rotation of the dose adjustment dial aligns one of a number of ribs provided on the dial with a rib on the plunger. The stroke of the plunger is limited by the length of the selected rib.
Detents are provided which tend to stop the dial at preselected angular positions which correspond to required dose volumes. However, excluding the resistance provided by the detents, the dial can be freely rotated at any time. This may lead to a user accidentally or inadvertently changing the dose, and therefore providing an animal with a suboptimal dose of remedy.
The terms “animal remedy” and “remedy” are used herein to include any preparation which may be administered to an animal and includes drugs, medicines, remedies, therapeutic preparations and the like.
The term “dose” is used herein to denote the volume of liquid dispensed by a dispensing means with a single stroke of a piston or plunger, except where the context clearly requires otherwise.
Where an angle between two axes is quantified, the angle measured is the acute angle, rather than the obtuse angle.